Tumor cells express a variety of gene products that provoke innate and adaptive immune recognition, and the formation of clinically evident tumors can indicate a failure of host defense. One mechanism that facilitates tumor progression is insufficient tumor antigen presentation. The therapeutic effects of many antibodies used to treat cancer have been found to arise from the recruitment of immune effector cells by engaging Fc receptors (Nimmerjahn and Ravetch, Curr. Opin. Immunol. 19:239-245, 2007). Cancer remains a major cause of human morbidity and mortality, and there is a continuing need for therapeutic strategies that consistently stimulate protective immunity.